This invention relates to microwave apparatus for heating food and other material bodies, and more particularly to improved, more easily manufactured microwave heating apparatus with multiple energy couplers and solid state power sources.
In the ordinary microwave oven a single high power microwave generator such as a magnetron tube is used in conjunction with a single coupler or antenna element, and the energy fills the entire oven cavity. There are difficulties at present with various schemes to use a plurality of low power sources such as microwave solid state devices. Although it is possible to combine the individual power outputs of a few low power sources into a single transmission line, the total power that can be produced is limited and is best utilized as the equivalent of a single higher power source. If multiple energy couplers are used in conjunction with a plurality of independent low power microwave sources, the problem to be overcome is that the individual sources may destructively interfere with one another.
In concurrently filed application Ser. No. 645,795 by John Maurer entitled "Microwave Heating Apparatus with Multiple Coupling Elements and Microwave Power Sources," assigned to the same assignee as this invention, a microwave heating apparatus is disclosed which operates on the principle that energy generated by each power source is coupled to a different region of the body being heated and is substantially absorbed by the material to thereby provide isolation between coupling elements and hence power sources. The surrounding conductive enclosure tube is cut off and can be extended lengthwise so that higher order mode energy decays and continuous processing operations are possible. The preferred embodiment is a frankfurter warmer with cylindrical enclosure and dielectric load support tubes and several axially spaced helical coupling elements that are partially wrapped about the support tube with a smooth curving transition between the two tubes for low reflection. A rectangular configuration for industrial heating applications is also described. The present invention relates to improvement and further development of this type of microwave heating apparatus.